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Paramagnetism in Pb(Zr,Ti)O3 nanotube arrays at low temperatures
부상돈,한진규,최용찬,양선아 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.7
The nano-ferroelectrics community has taken a keen interest over the past 65 years in achieving the toroidal (circular) ordering of electric domains. Understanding the behavior of vortex ferroelectric domain states remains an unresolved issue because electric polarization density interactions contribute significantly to large extrinsic effects if the strain, charge and size are not tightly controlled. Here, we present an experimental clue to toroidal ordering at low temperatures, that is, the paramagnetism in highly-ordered arrays of ferroelectric Pb(Zr,Ti)O3 nanotubes composed of nanometer-sized perovskite crystallites. The critical temperature for the phase transition from a normal ferroelectric polar state to toroidal ordering is 70 K.
부상돈,최용찬,한진규,양선아,김종옥 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.31
We present a systematic analysis of the nanotube-synthesis method of template-directed growth in conjunction with the sol-gel process and a spin-coating technique (TSS). Advantages and disadvantages of the TSS method are described. The method is a simple, highly reproducible, and time-saving method to prepare multi-functional complex metal-oxide nanotubes with high aspectratios. However, the method still has delicate problems to be solved: the low-solid content of the sol-gel precursor solution, the interaction between the surfaces of the pore walls of the porous alumina template (PAT) and the sol particles, and the unwanted interaction between the PAT and the deposited sol-gel solution. Precise control of the experimental parameters, such as the pH of the precursor solution, the volume of the drop during the spin-coating process, the spinning speed, and the spinning time, is needed.
부상돈,Bu Sang Don 한국진공학회 2004 Applied Science and Convergence Technology Vol.13 No.4
RF magnetron sputtering 방법으로 miscut된 기판을 이용해서 양질의 압전 산화물 에피 박막을 제작하였다. 박막은 (001) $SrTiO_3$ 기판 위에 증착되었으며, (100) 방향으로 $0^{\circ}$-$8^{\circ}$의 miscut 각도를 갖는 기판들을 사용했다. $4^{\circ}$이상의 큰 miscut 각도를 갖는 기판 위에 성장된 박막의 경우, x-ray diffraction (XRD) 패턴은 perovskite 상의 순수한 PMN-PT 피크만을 보여 주었으며, wavelength dispersive x-ray fluorescence spectroscopy를 이용해서 분석한 조성비는 stoichiometric한 조성비에 가까운 값을 보여주었다. 반면에, miscut 각도가 없는 기판 위에 증착된 박막의 경우, 2차상인 pyrochlore 상을 포함하는 XRD 패턴을 보여주었다. $8^{\circ}$ 기판 위에 성장된 박막의 경우 실온에서 20$\mu$C/$\textrm{cm}^2$라는 높은 잔류분극 값을 보여주었다 We have grown piezoelectric oxide films by RF magnetron sputtering using miscut substrates. Films were Brown on(001) $SrTiO_3$ substrates with miscut angles from 0 to 8 degrees toward the (100) direction. Films on high miscut substrates (>$4^{\circ}$) showed almost the pure perovskite phase in x-ray diffraction and were nearly stoichiometric. In contrast, films on exact (001) $SrTiO_3$ contained a high volume fraction of pyrochlore phases. A film on an $8^{\circ}$ miscut substrate exhibits a polarization hysteresis loop with a remnent polarization of 20$\mu$C/$\textrm{cm}^2$ at room temperature.